Boron hydride salts, in particular the non-metal salts of decahydrodecaboric acid, had been discovered to have particular utility in the field of high energy fuels. They may be used as constituents of pyrotechnic compositions and in propellants. For example, non-metallic salts of the decahydrodecaborate ion, and exemplary uses, are disclosed in the copending applications of common assignment entitled IGNITION AND PYROTECHNIC COMPOSITIONS, Ser. No. 694,625, filed June 10, 1976, and COPRECIPITATED PYROTECHNIC COMPOSITION PROCESSES AND RESULTANT PRODUCTS, Ser. No. 694,626, filed June 10, 1976.
The present invention teaches new non-metal salts of decahydrodecaboric acid, which exhibits stable physical properties, and are themselves high energy monopropellants. The compounds are very unusual in that they contain only boron, nitrogen, carbon and hyrogen, but no oxygen.
A particular objective in preparing compounds suitable for certain types of pyrotechnic usage is to achieve a high gas output and low molecular weight combustion products, when the compound is burned. Combustion products such as hydrogen (H.sub.2) and nitrogen (N.sub.2) gas fulfill this requirement. In preparing salts useful as pyrotechnic fuels from an anion such as decahydrodecaborate (-2) (B.sub.10 H.sub.10.sup.-2), it has been found advantageous to use a cation containing a high weight fraction of atomic nitrogen and hydrogen. Cations of the general formula C(NHR).sub.3 where R may be hydrogen (H) or an amino radical (--NH.sub.2) are found to be such cations. In addition, the corresponding Bronsted bases of the free ions are strong bases, thus imparting to the cations and therefore the salts a high degree of chemical stability.
Other decahydrodecaborate (-2) salts employing guanidine chemistry have been previously investigated by the present inventor. The simple guanidine salt is disclosed in my earlier application BIS-GUANIDINIUM DECAHYDRODECABORATE AND A PROCESS OF ITS PREPARATION, Ser. No. 694,627, filed June 10, 1976, which is now U.S. Pat. No. 4,002,681. This simple salt was found to be useful as a high energy pyrotechnic fuel, and was by itself thermochemically stable; i.e., it has a substantial negative heat of formation as commonly defined by those practiced in the art. The fully amino-substituted compound is disclosed in my copending application of common assignment entitled BIS-TRIAMINOGUANIDINIUM DECAHYDRODECABORATE AND A PROCESS FOR ITS PREPARATION, Ser. No. 762,229, filed Jan. 24, 1977. In contast to the simple guanidine salt, the triaminoguanidine salt is a powerful monopropellant; i.e., combusts by itself releasing internal energy, without need of additional oxidizer materials.
The subject of the present invention is the mono- and diamino substituted guanidine salts, which like the triaminoguanidine salts, have been discovered to be monopropellants. As a result, the compounds taught herein are useful as monopropellants in their own right, or alternatively, can be used with additional oxidizer to modify combustion properties. Specifically, such inorganic oxidizing agents as potassium nitrate, guanidine nitrate, triaminoguanidine nitrate and ammonium perchlorate may advantageously be employed, in concentrations from 0-90%, by weight.